Kant's Transcendental Arguments

Among Immanuel Kant's (1724–1804) most influential contributions
to philosophy is his development of the transcendental argument. In
Kant's conception, an argument of this kind begins with a compelling
premise about our thought, experience, or knowledge, and then reasons
to a conclusion that is a substantive and unobvious presupposition and
necessary condition of this premise. The crucial steps in this
reasoning are claims to the effect that a subconclusion or conclusion
is a presupposition and necessary condition of a premise. Such a
necessary condition might be a logically necessary condition, but
often in Kant's transcendental arguments the condition is necessary in
the sense that it is the only possible explanation for the premise,
whereupon the necessity might be weaker than logical. Typically, this
reasoning is intended to be a priori in some sense, either
strict (Smit 1999) or more relaxed (Philip Kitcher 1981, Pereboom
1990). The conclusion of the argument is often directed against
skepticism of some sort. For example, Kant's Transcendental Deduction
targets Humean skepticism about the applicability of a priori
metaphysical concepts, and his Refutation of Idealism takes aim at
skepticism about external objects. These two transcendental arguments
are found in the Critique of Pure Reason (1781, 1787), but
such arguments are found throughout Kant's works, for example in
the Critique of Practical Reason (1788), in the Critique
of the Power of Judgment (1790), and in the Opus
Posthumum (Förster 1989). This article focuses on the
Transcendental Deduction, the Refutation of Idealism, and more recent
transcendental arguments such as P. F. Strawson's (1966) that are
inspired by these two examples.

The Transcendental Deduction (A84–130, B116–169) is Kant's
attempt to demonstrate against empiricist psychological theory that
certain a priori concepts correctly apply to objects featured
in our experience. Dieter Henrich (1989) points out that Kant's use of
‘Deduktion’ redeploys German legal vocabulary; in
Holy Roman Empire Law, ‘Deduktion’ signifies an
argument intended to yield a historical justification for the
legitimacy of a property claim. In Kant's derivative epistemological
sense, a deduction is an argument that aims to justify the use of a
concept, one that demonstrates that the concept correctly applies to
objects. For Kant a concept is a priori just in case its
source is the understanding of the subject and not sensory experience
(A80/B106; Strawson 1966: 86). The specific a priori concepts
whose applicability to objects of experience Kant aims to vindicate in
the Transcendental Deduction are given in his Table of Categories
(A80/B106); they are Unity, Plurality, and Totality (the Categories of
Quantity); Reality, Negation, and Limitation (the Categories of
Quality); Inherence and Subsistence, Causality and Dependence, and
Community (the Categories of Relation), and Possibility-Impossibility,
Existence-Nonexistence, Necessity-Contingency (the Categories of
Modality).

David Hume in effect denies that a deduction can be provided for a
number of metaphysical concepts — ideas, in his
terminology — including the ideas of personal identity, of
identity over time more generally, of the self as a subject distinct
from its perceptions, and of causal power or force (1739, 1748). In
Hume's view, a concept can only be validated by finding a sensory
experience, that is, an impression, in particular the one
that is the ‘original’ of that idea, which must resemble
that idea. But because, for example, any attempt to find an impression
of causal power turns out to be fruitless, Hume concludes that this
idea does not legitimately apply (1748: §7). In Kant's
terminology, Hume is determining whether one might provide
an empirical deduction of the concept of causal power
(A85/B117), and from the failure of the attempt to do so, he concludes
that this concept lacks objective validity, that is, it does
not apply to the objects of our experience.

Hume's position on the deducibility of a priori metaphysical
concepts is Kant's quarry in the Transcendental Deduction. But Kant
concurs with Hume's proposal that no empirical deduction can be
supplied for such concepts. Instead, he sets out to provide a
different sort of justification for their use, one that
is transcendental rather than empirical. Such a
transcendental deduction begins with a premise about any possible
human experience, a premise to which reasonable participants in the
debate can be expected initially to agree, and then contends that a presupposition and necessary condition of the truth of that premise is the applicability
of the a priori concepts in question to the objects of
experience. Kant's Transcendental Deduction features a number of
component transcendental arguments. Each begins with a premise either
about the self-attributability of mental items, apperception,
or else a premise about the necessity and universality of some feature
of our experience of objects. Kant strategy is then to establish a
theory of mental processing, synthesis, by arguing that its
truth is a necessary condition for the truth of such a premise, and
then to show that the a priori concepts at issue -- the
categories -- have an essential role in this sort of mental
processing. On a metaphysical idealist interpretation of his position,
the objects of experience result from this mental processing, and it is
due to the role that the categories have in this processing that they
correctly apply to objects. In the Transcendental Deduction Kant would
thus intend to secure a normative claim, that the categories correctly
apply to the objects of our experience, by establishing a
psychological theory (Henrich 1989; Patricia Kitcher 1990: 2–29;
for information on related argumentative strategies in Kant's
historical context, see Kuehn 1997 and Dyck 2011). The Transcendental
Deduction presents general considerations supporting the applicability
of all the categories to the objects of our experience; it does not
concentrate on the applicability of specific categories. This more
focused task is taken up in various sections of the Analytic of
Principles (A130–235/B169–287).

In the Metaphysical Deduction (A66–83, B92–116)
Kant intends to derive the categories from the specific modes or forms
of any human thought about the world, the logical forms of
judgment. The Metaphysical Deduction has an essential role to
play in the Transcendental Deduction, and we will discuss this
argument at an appropriate juncture (when we reach §19 of the
B-Deduction).

For Kant, the most significant rival theory of mental processing is
that of his target, Hume. Hume concurs that a theory of experience
requires an account of the processing of mental items, but he denies
that such an account demands a priori concepts or issues in
their legitimate applicability to experience. According to his theory,
associationism, our mental repertoire consists solely of
perceptions, all of which are sensory items — the more vivid
impressions, which constitute sensory experience, and their less vivid
copies, the ideas, which function in imagination, memory, reasoning,
and conceptualization (1748, §§2, 3). Association is the
process by which these perceptions are related and ordered. A
signature feature of association on Hume's view is that it requires no
resources distinct from the perceptions themselves. How perceptions
are ordered is solely a function of what perceptions alone can
provide. Significantly, a subject not constituted solely of
perceptions has no role in Hume's theory; the Humean subject is just a
collection of perceptions (1739: I, IV, vi). These last two features
in particular make Humean associationism a highly economical theory,
which provides it with an initial advantage over Kant's more complex
view. However, Kant contends that associationism cannnot account for
the facts to which the premises of the Transcendental Deduction
appeal, and that synthesis by a priori concepts, that is, the
categories, is required in addition.

Kant characterizes synthesis as “the act of putting
different representations together, and grasping what is manifold in
them in one cognition” (A77/B103); it is a process that “gathers the
elements for cognition, and unites them to form a certain content”
(A78/B103). Synthesis takes multiple representations — in
Kant's terminology, a ‘manifold’ — and connects them
with one another to produce a single further representation with
cognitive content (Patricia Kitcher 1990, 2011). This process employs
concepts as modes or ways of ordering representations. A claim critical
to the Transcendental Deduction is that it is the categories by means
of which manifolds of our representations are synthesized. Since the
understanding of the subject is the source of the categories, and also
a faculty that yields synthesis, the subject plays a crucial role in
mental processing. It is important for Kant's view on mental
processing that this subject is distinct from its representations, and
this is another respect in which it differs from Hume's
theory.

This discussion will focus on the Transcendental Deduction in the
second edition of the Critique of Pure Reason (1787) —
the B-Deduction — thoroughly rewritten and rethought
relative to the A-Deduction of the first edition (1781). On
my reading, in §§16–20 of the B-Deduction Kant employs
a two-pronged strategy for defeating associationism and establishing
synthesis. The first, contained in §§15–16, is
designed to show that association cannot account for an aspect of
one's consciousness of one's self that Kant refers to as the
consciousness of its unity, and that synthesis is required to
provide this explanation. This type of argument he calls
an argument from above, signifying that it begins with a
premise about self-consciousness. Correlatively, in
§§17–20 we find an argument from below, by
which Kant intends to establish that synthesis by means of the
categories is needed as a necessary condition of how we represent
objects (the above/below terminology is derived from A119; for
relevant historical background, see Carl 1989, 1992). On several other
readings, as we shall see, the B-Deduction is a more unified
argument. There are reasons to accept and reasons to resist
interpretations of this kind.

The argument from above in §16 can be divided into two
stages. The goal of the first is to establish the various components
of the principle of the necessary unity of apperception. The
second stage aims to show that synthesis is a necessary condition for
the aforementioned aspect of self-consciousness, which this principle
highlights. Apperception is the apprehension of a mental
state – a representation, in Kant's terminology – as one's
own; one might characterize it as the self-ascription or
self-attribution of a mental state (Strawson 1966: 93–4). In
Kant's conception, my apperception has
necessary unity since all of my representations
must be grounded “in pure apperception, that is, in the
thoroughgoing identity of the self in all possible
representations” (B131–2, emphasis mine). By this he means
that:

(The principle of the necessary unity of apperception) It
must be the case that each of my representations is such that I
can attribute it to my self, a subject which is the same for all of my
self-attributions, which is distinct from its representations, and
which can be conscious of its representations (A116, B131–2,
B134–5).

One might note three aspects of the meaning of this principle. First,
as pointed out earlier, Kant maintains that the apperceiving subject is not
itself a collection of representations. Kant affirms that I have no
inner intuition of the subject (e.g. B157), and this claim would
conflict with the subject's being a collection of representations,
since he holds that I can intuit my representations by inner sense
(e.g. A33/B49). Also, in §16 Kant remarks: “through the
‘I’, as simple representation, nothing manifold is given;
only in intuition, which is distinct from the ‘I’, can a
manifold be given” (B135). If he believed the apperceiving
subject to be a collection of representations, it would be surprising
for him to deny that anything manifold is given through my
representation of it. Second, my ability to attribute representations
to myself as subject of them is pure, as opposed
to empirical apperception. This means that I have this
ability not in virtue of Humean inner perception, or Kantian inner
intuition, but rather independently of any such empirical
faculties. However, Kant repeatedly affirms that the purity of this
apperception does not imply that the subject to which one's
representations can be attributed is intuited — represented as
an object — in a purely rational or a priori way (e.g.,
B406–9). Third, Kant states that pure apperception
is original, and the explication he provides is that
“it is that self-consciousness which, while generating the
representation ‘I think’ … cannot itself be
accompanied by any further representation” (B132). I cannot have
an intuition or any other type of representation of myself as
apperceiving subject other than by way of ‘I
think…’- type thoughts, and hence these thoughts are the
original representations of this subject (e.g., A350). At the same
time, by virtue of my capacity for apperception, I can have a kind of
propositional grasp of the apperceiving subject; Kant affirms that in
apperception, I am conscious that I exist as subject
(B157).

Kant initiates the first stage of the argument in §16 by
claiming:

It must be possible for the ‘I think’ to accompany all my
representations; for otherwise something would be represented in
me which could not be thought at all, and that is equivalent to saying
that the representation would be impossible, or at least would be
nothing to me. (B131–32)

On one interpretation, the sense in which a representation would be
impossible or nothing to me if it could not accompanied with the
‘I think’ is simply that I could not then become conscious
of it (Guyer 1987: 139–44). It is credible that for any
representation of which I am conscious, I can attribute it to
myself as subject, assuming my mental faculties are in working order,
and if no controversial account of the nature of the subject is
presupposed. However, the claim that I can become conscious of
each of my representations, and that it is therefore possible
for me attribute each of them to myself as their subject, is likely
false. Plausibly, some of my representations are so thoroughly
subconscious that I cannot attribute them to myself, while they are
nevertheless mine due to the causal relations they bear to other
representations and to actions that are paradigmatically
mine. Fortunately, however, the premise that each of my
representations is such that I can attribute it to myself is not
crucial for the argument from above. Rather, the premise Kant
ultimately singles out is less committed, and focuses more
specifically on the identity or sameness of the subject of different
self-attributions, and my being conscious of this identity.

A number of interpreters, including Robert Howell (1992) and James van
Cleve (1999), maintain that the argument of §16 requires a premise
affirming the possibility of my being simultaneously conscious
of the multiple elements of my representations, and that the implausibility
of this premise jeopardizes the soundness of the argument.
Howell's specific objection is that Kant does not
establish the following crucial premise:

(S) All of the elements of the manifold of i (where i is
some arbitrary intuition) are such that H is or can become conscious,
in thought, that all of those elements, taken together, are
accompanied by the I think.

(S) asserts that all of the individual elements of the selected
intuition are such that the subject is or can become conscious of them
simultaneously. In Howell's interpretation, only if the elements of an
intuition together and at the same time are accompanied by the
same I think will it be plausible that the subject must
synthesize these elements (Howell 1992: 162). On van Cleve's reading,
it is required that for any intuition that I have, I actually become
simultaneously conscious of its elements. If this co-consciousness
were just merely possible, Kant could only conclude is that the
resulting representation is only possibly subject to the categories
(van Cleve 1999: 84). On an interpretation of this type, the mechanism
of the argument of §16 is to adduce a kind of unity or
combination that my representations actually exhibit, and then to
argue that this unity requires synthesis by means of the categories as
a condition or for its explanation. Kant is thus read as contending
that actual co-consciousness is a type of unity that demands synthesis
by means of the categories, and that any variety of unity short of
co-consciousness will be inadequate to establishing this objective of
the Deduction.

Howell points out that (S) contrasts with a weaker claim:

(W) Each element of the manifold of i is such that H is or can
become conscious, in thought, that the I think accompanies
that element. (Howell 1992: 161)

which allows that the individual elements of the intuition are such
that the subject can only become conscious of each separately, perhaps
in turn. He contends, however, that the unity expressed by (W) is
insufficient to generate this need for synthesis. If I am merely
(possibly or actually) serially conscious of the elements of an
intuition, it won't be required that I synthesize them into a unified
intuition. Howell goes on to argue that while (W) is credible, Kant
cannot in fact establish (S); it is implausible that such
co-consciousness for any arbitrary intuition is actual or even
genuinely possible for us. Consequently, the soundness of this
argument, and the overall argument of the B-Deduction is
imperiled.

However, it may be that only the weaker premise (W) is required for the
success of the argument of §16. First, although the
co-consciousness premise (S) might be suggested in §16 by
the following text:

That relation comes about, not simply through my accompanying each
representation with consciousness, but only in so far as I conjoin one
representation with another, and am conscious of the synthesis of them
(B133)

that claim is not uncontroversially made here. For by the assertion
that I “am conscious of the synthesis of them,” i.e., of
these representations, Kant may mean only that I am conscious that
they stand in a certain intimate relation to one another, for
instance, that that they are integrated with each other in a way
distinct from how mine are integrated with yours, which does not
require co-consciousness (Pereboom 1995).

Moreover, it might well be that the argument of §16 features a
subtlety that obviates the need for actual co-consciousness. The text
indicates that the argument crucially turns on the claim that
only a priori synthesis – that is, synthesis by a
priori concepts – can explain how I might represent the
identity of my apperceptive consciousness (B133) or how I
might represent the identity of the apperceiving subject (B135)
for different elements of the manifold of intuition to which I can
attach the I think. The inadequacy Kant claims for
“empirical consciousness,” that is, for consciousness
according to Humean psychological theory, is that “it is in
itself dispersed (an sich zerstreut) and without relation to
the identity of the subject (und ohne Beziehung auf die
Identität des Subjects)” (B133). One implication of
this passage is that Hume's theory does not have the resources needed
to explain how I can self-attribute various of my representations or
their elements to a subject that is both conscious of them and the
same subject for each act of their self-attribution. This objection
does not beg the question in Kant's dispute with Hume, since it
assumes only a claim that uncommitted and reasonable participants in
this discussion would not want to initially deny, that the conscious
subject of these apperceptive self-attributions is the same. Hume's
theory lacks the resources to account for this identity. Hume himself
provides no account of apperception, but possibilities for a Humean
account are that apperceptive consciousness amounts to perceptions
that are intrinsically self-conscious, or else consists in perceptions
of perceptions. But intrinsically self-conscious perceptions would be
distinct from one another, as would perceptions of perceptions; and
thus they too would be “dispersed” (B133), and share no
common element. Hume might propose to explain our sense of the
identity of the conscious subject of different self-attributions by
the intrinsically self-conscious perceptions or the perceptions of
perceptions being components of a single causally coherent
bundle. However, this bundle would not itself be conscious of
perceptions. Consciousness of perceptions would instead be an
intrinsic feature of an individual self-conscious perception or a
feature of individual perceptions of a perception. In Kant's
conception, by contrast, accounting for our sense of the identity of
the conscious subject of different self-attributions requires that
this subject be distinct from its representations.

The second stage of the argument of §16 highlights another
implication of the claim that “the empirical consciousness,
which accompanies different representations, is
dispersed and without relation to the identity of the subject” (B133):
that Hume's theory lacks the resources to account for my
representation-relation to the identity of the subject; that
is, this view cannot explain how I can “represent to myself
the identity of the consciousness in [i.e. throughout] these
representations” (B133) (for an opposing view see Dickerson
2004: 95-8). We might imagine several kinds of explanation for my
representation of this identity. One candidate is that inner sense
allows me to represent this identity: the way I represent the sameness
of the subject is akin to how I commonly represent the identity over
time of ordinary objects — by a cognitive sensitivity to
similarities among the intrinsic properties represented. However, Kant
and Hume concur that this is not how I might represent the identity of
the apperceiving subject, since they agree that by inner sense I
cannot represent any intrinsic properties of such a subject. A second
kind of explanation, which Kant endorses, is that I have an indirect
way of representing this identity. This representation must instead
depend on my apprehending a feature of my representations (or elements
of them) (Allison 1983: 142–4; Guyer 1977: 267, 1987:
133–39; Patricia Kitcher 2011:147). The appropriate feature is a
type of unity or ordering of these states. The idea is that if the
representations I can attribute to myself possess a unity of the right
kind, and if I apprehend or am cognitively sensitive to this unity,
then I will be able to represent the apperceiving subject of any one
of them as identical with that of any other.

Thus my representation of the identity of the subject comes about “only
in so far as I conjoin one representation with another, and am
conscious of the synthesis of them” (B133). This consciousness is
profitably interpreted as conscious awareness not of the act or process
of synthesis itself, but rather of the unity that is its outcome
(Strawson 1966: 94–6; Dicker 2004: 133–4)). What sort of unity must I
consciously recognize among my representations that would account for
my representation of this identity? Note that it is not plausibly
co-consciousness, for I represent the subject as identical for
self-attributed representations that are not co-conscious, so actual
co-consciousness could not explain generally how I represent this sort
of identity. A credible alternative is that the unity consists in
certain intimate ways in which representations in a single subject are
typically related. Arguably, the essential feature of this unity is
that a single subject's representations be inferentially and causally
integrated to a high degree, and in this respect they are unified in a
way in which representations possessed by discrete subjects are not.
Alternatively, several commentators have argued that
the relevant unity might be a temporal order among my representations,
thereby linking the B-Deduction with the arguments of the Second
Analogy and the Refutation of Idealism (Guyer 1977: 267; Dicker 2004:
137–44). A concern about this route is that a cognitive sensitivity to
the time-ordering of representations does not obviously facilitate our
representing them as belonging to a single subject (Brueckner 1984:
199–208). By contrast, when mental states fail to exhibit inferential
and causal integration, as in the case of multiple-personality
disorder, we have a tendency to posit multiple subjects, while we do
not do so when such integration is present.

In Kant's view, the candidates for explaining how this kind of unity
comes to be, or, less ambitiously, for explaining my ability to
recognize this sort of unity, are association and synthesis. At this
point he appears to suppose that because Hume's psychological theory
has already been ruled out, synthesis is the only remaining option. So
for me to represent the identity of the subject of different
self-attributions, I must generate or at least recognize the right
sort of unity among these representations, and synthesis must be
invoked to account for this unity. Thus Kant contends that this
combination “is an affair of the understanding alone, which
itself is nothing but the faculty of combining a
priori” (B134–5. Since the understanding provides
concepts for synthesis, and because for synthesis to be a
priori is, at least in part, for it to employ a priori
concepts, Kant is contending here that synthesis by means of a
priori concepts is required to account for the unity in
question.

Here is an austere representation of the structure of the argument
so far:

I am conscious of the identity of myself as the subject of
different self-attributions of mental states. (premise)

I am not directly conscious of the identity of this subject of
different self-attributions of mental states. (premise)

If (1) and (2) are true, then this consciousness of identity is
accounted for indirectly by my consciousness of a particular kind of
unity of my mental states. (premise)

This consciousness of identity is accounted for indirectly by my
consciousness of a particular kind of unity of my mental states. (1,
2, 3)

If (4) is true, then my mental states indeed have this particular
kind of unity. (premise)

This particular kind of unity of my mental states cannot be
accounted for by association. (5, premise)

If (6) is true, then this particular kind of unity of my mental
states is accounted for by synthesis by a priori
concepts. (premise)

This particular kind of unity of my mental states is accounted for
by synthesis by a priori concepts. (6, 7)

Premise (1) is intended as a claim the skeptic about the legitimate
applicability of a priori concepts will at least initially
accept. The crucial necessary conditions, expressed by (3) and (7),
are necessary conditions of only possible explanation. However, Paul
Guyer forcefully argues that establishing the need for synthesis by
means of a priori concepts would require ruling out the
alternative explanation that empirical information and concepts
derived from it is sufficient to account for the recognition of the
unity at issue (Guyer 1987:146–7). And in his view it remains
open, given what Kant has shown, that this recognition requires only
awareness of information derived from inner sense or introspective
experience. Kant does not attempt at this point in the argument to
rule out such a rival empiricist hypothesis, but he arguably would
need to do so to establish the need for a priori
synthesis. To advance his claims, one might appeal to features of this
unity that would render such an empiricist account inadequate. As we
shall see, Kant employs this tactic in the next phase of the argument,
which introduces his account of our representations of objects.

According to one widespread reading of the B-Deduction,
§§15–20 comprise a an argument whose only assumption
is the premise about self-consciousness that Kant defends in §16.
Strawson, for example, is a proponent of such an interpretation
(1966), as are Robert Paul Wolff (1963), Jonathan Bennett (1966),
Henry Allison (1983), Edwin McCann (1985), and Dennis Schulting
(2013). Demonstrating that we represent objects or an objective world
has a key role in most versions of this reading. On Strawson's interpretation, for
instance, “the fact that my experience is of a unified objective
world is a necessary consequence of the fact that only under this
condition could I be conscious of my diverse experiences as one and
all my own” (1966: 94). Some interpreters dissent; Karl Ameriks,
for example, contends that Strawson's conception of the Deduction is
motivated by a desire to see it as showing that the skeptic about the
external world is mistaken, while in fact refuting this sort of
skeptic is not one of Kant's aims for this argument (Ameriks 1978,
Allais 2011). Patricia Kitcher (2011: 115–18) argues against the
single premise about self-consciousness interpretation on historical
and textual grounds.

An uncontroversial role of §17 is to provide a characterization
of an object, or more to the point, of a representation of an object,
that facilitates a challenge to Humean associationism. Kant's proposal
is that an object is “that in the concept of which a manifold of
a given intuition is united” (B137). Here ‘object’
should be read in the broad sense of objective feature of reality
— a feature whose existence and nature is independent of
how it is perceived (B 142; Bird 1962/1973 130–31; Strawson 1966:
98–104; Guyer 1987: 11–24). Allison is a proponent of the
view that §17 contain not only this challenge to Hume, but also
an attempt to demonstrate that we represent objects on the basis of
the conclusions about self-consciousness established in §16. This
interpretation is a component of Allison's broader vision of the
B-Deduction, according to which Kant demonstrates that the unity of
apperception entails that we represent objects, and, conversely, that
our representing objects entails the necessary unity of apperception
(Allison 1983: 144ff.) Indeed, the crucial claim for Allison's
interpretation is that the unity of apperception is not only a
necessary but also sufficient condition for our representing of
objects. This he calls the reciprocity thesis. Other
commentators, including Richard Aquila (1989: 159), Howell (1992:
227–8) and Schulting (2013) agree that the B-Deduction features
the reciprocity thesis and an attempt to establish its truth, while
Ameriks (1978) disagrees. On an account of the sort Ameriks favors,
the unity of apperception, and more exactly, the synthesis that
explains our consciousness of the identity of the subject, is only a
necessary condition for the representation of objects (cf. Allais
2011).

Allison's interpretation is attractive particularly because it
promises leverage against the skeptic who denies that we represent
objects, and also because this leverage is generated by premises about
self-consciousness that this skeptic is likely to
accept. Nevertheless, there are textual and charitable reasons to
resist this reading (Ameriks 1978, Pereboom 1995; Patricia Kitcher
2011: 115-60). First of all, in §§18–20 Kant makes
significant assumptions about features of our representations of
objects that exceed anything that he has argued for in §17 or
earlier. In particular, §18 he assumes that our representations
of objects manifest a certain kind of necessity and universality, and
this he does not purport to establish in §17 or
earlier. Moreover, in the summary of the preceding steps of the
B-Deduction in §20 Kant does not include premises from
§§15–16. What we actually encounter in §20
indicates that Kant intends §§17–20, with some help
from §13, to constitute a single, self-contained argument that
does not depend on the conclusions about self-consciousness developed
in §§15–16.

On Allison's conception, the argument from the unity of
apperception (or, equivalently, from the unity of consciousness) for
our representing objects occurs in the following passage:

(A) Understanding is, to use general terms, the faculty of
cognitions (Erkenntnisse). They consist (bestehen) in
the determinate relation of given representations to an object:
and an object is that in the concept of which the manifold of a given
intuition is united. Now all unification of representations demands
unity of consciousness in the synthesis of them. Consequently it is the
unity of consciousness that alone constitutes the relation of
representations to an object, and therefore their objective validity
and the fact that they are cognitions (Erkenntnisse): and upon
it therefore rests the very possibility of the understanding.
(B137)

Allison himself presents a problem for his interpretation of this
passage. He contends, first of all, that the reciprocity thesis is
encapsulated in this sentence:

It is the unity of consciousness that alone constitutes
[ausmacht] the relation of representations to an object, and
therefore their objective validity.

and that Kant presents (1) as a direct consequence of the premise
that

all unification of representations demands unity of
consciousness in the synthesis of them.

Allison points out that on this reading Kant's reasoning appears to
involve a non sequitur, since (2) supports only Kant's having
in mind that the unity of consciousness is a necessary condition for
the representation of an object, and not for its also being a
sufficient condition. Howell raises a similar concern: “In
§17 Kant simply does not make this inference clear, and an air of
blatant fallacy hovers over this part of his reasoning” (Howell
1992: 228; for an opposing view see Keller 1998: 80). But Ameriks
argues that the B-Deduction should not be interpreted as providing an
argument for the sufficiency claim, and a respectable case can be made
for his reading (Ameriks 1978; Pereboom 1995; Patricia Kitcher 2011:
115-60).

Allison and Howell both argue that (1) should be read as a statement
of the sufficiency claim. Now in (A) Kant contends that cognitions of
objects consist in a determinate relation of representations to
objects, and as (1) indicates, this relation is constituted or produced
by a synthesis that essentially involves the unity of consciousness.
However, (1) does not indicate that the synthesis that involves unity
of consciousness cannot occur without its resulting in a relation
of a representation to an object. By analogy, the smelting and molding
of steel are processes that constitute or produce steel girders,
but from this one should not conclude that the processes of
smelting and molding steel cannot take place without the production of
steel girders. Just as producing steel girders also requires molds of
particular shapes, so producing representations of objects might
require, in addition to the synthesis that involves the unity of
consciousness, particular concepts of objects.

If the sufficiency claim, and with it the reciprocity thesis, is
denied, we need an alternative account of how §17 functions in
the overall argument of the B-Deduction. It may be that the role of
this section is largely to provide a characterization of an object
that has a key role in the ensuing challenge to Humean associationism, and
thereby initiates an argument from below. Kant's proposal is that an
object is “that in the concept of which a manifold of a given
intuition is united” (B137). The subsequent claim is that the
unification of a manifold requires synthesis; immediately following
the characterization of an object he states that “all
unification of representations demands unity of consciousness in the
synthesis of them” (B137). It seems consistent with these texts
that Kant's characterization of an object is designed just to present
his anti-Humean theory of the mental processing required for
representing objects, and that the subsequent claim for the need for
synthesis does not express a view he expects us to accept without
further argument, but rather one he aims to confirm in
§§18–20. If this argument succeeds, it will turn out
that the a priori synthesis required to account for the
features of our representations of objects Kant singles out is the
same process that yields my consciousness of the identity of myself as
subject of different self-attributions.

In §18 Kant draws our attention to certain features of our
representations of objects that, in his view, will serve to defeat
associationism and establish a priori synthesis:

The transcendental unity of apperception is that unity through which
all the manifold given in an intuition is united in a concept of the
object. It is therefore entitled objective, and must be
distinguished from the subjective unity of consciousness…
Whether I can become empirically conscious of the manifold as
simultaneous or as successive depends on circumstances and empirical
conditions. Therefore, the empirical unity of consciousness,
through association of representations, itself concerns an
appearance, and is wholly contingent… Only the original
unity is objectively valid: the empirical unity of
apperception,… which… is merely derived from the former
under given conditions in concreto, has only subjective
validity. One person connects the representation of a certain word
with one thing, the other [person] with another thing; the unity of
consciousness in that which is empirical is not, as regards what is
given, necessarily and universally valid. (B139–40)

For Kant, a defining feature of our representations of objects is
their objective validity. For a representation to be objectively valid
it must be a representation of an objective feature of reality, that
is, a feature whose existence and nature is independent of how it is
perceived (Guyer 1987:11–24). In this argument, it appears that
Kant just assumes that the representations that make up experience are
objectively valid. He then aims to establish that association is
inadequate because it can yield only representations that are not
objectively valid. In the above passage, Kant contends that our
objectively valid representations must in a sense be necessary and
universal. However, the empirical unity of consciousness, which
involves an ordering of representations achieved by association, can
only be non-universal, contingent, and hence merely subjectively
valid, by contrast with the transcendental unity of apperception,
which involves an ordering that is universal and necessary, and is
therefore objectively valid. In Kant's conception, it is the fact that
the transcendental unity of apperception is generated by a
priori synthesis that allows it to yield an ordering that is universal, necessary, and objectively valid. (Ameriks 1978, Pereboom 1995, Patricia Kitcher
2011:115-60; Allais 2011)

To illustrate and support these claims, Kant invokes
examples of the ordering of phenomena in time that also have the key
role in the discussion of the Second Analogy (cf. Guyer 1987: 87–90;
Dicker 2004: 137–44). There Kant argues that our representations,
considered independently of their content, are always successive.
For example, when I view the front, sides, and back of the house when
walking around it, and when I watch a boat float
downstream, my representations of the individual parts and states occur
successively. The objective phenomena represented by these successive
representations, however, can be represented as either successive or as
simultaneous — I represent the positions of the boat as successive,
but the parts of the house as simultaneous. More precisely, despite the
representations in each of these sequences being subjectively
successive, I represent the parts of the house as objectively
simultaneous, and the positions of the boat as objectively
successive. How do we account for this difference in objectivity
despite the similarity in subjectivity? (Melnick 1973: 89)

The important clue for answering this question is that these
representations of objective simultaneity and succession are universal
and necessary. It is the universality and necessity of our representing
the parts of the house as simultaneous that accounts for our
representing them as objectively simultaneous, and the universality and
necessity of our representing the positions of the boat as successive
that accounts for our representing them as objectively successive.
Association is inadequate for accounting for this objectivity because
it is incapable of yielding such universality and necessity, a defect
not shared by synthesis.

A first approximation of the import of ‘universal’ in the house
example is:

(U) Any human experience of the parts of the house is an experience
of these parts as objectively simultaneous.

The addition of necessity has the following effect on (U):

(U-N, first pass) Necessarily, any human experience of the parts of
the house is an experience of these parts as objectively
simultaneous.

This claim would be resisted by Hume if the necessity were specified
as ranging over all possible circumstances, for Hume's theory
would allow for the possibility of a deviant ordering in unusual
empirical conditions. But (U-N, first pass) can be reformulated more
precisely as

(U-N) Necessarily, if empirical conditions are normal, any human
experience of the parts of the house is an experience of these
parts as objectively simultaneous.

Kant's view is that given only the resources of association, the truth
of (U-N) cannot be explained. The reason is “whether I can
become empirically conscious of the manifold as simultaneous or as
successive depends on circumstances or empirical conditions,”
and so “the empirical unity of consciousness, through
association of representations, itself concerns an appearance, and is
wholly contingent” (B139–40). Association cannot explain
the truth of (U-N), for given only the resources of association, the
parts of the house will not necessarily or universally be represented
as objectively simultaneous even supposing only normal empirical
conditions. Kant asks us to consider an activity, word association,
which functions as a paradigm for association. Word association,
familiarly, does not yield universal and necessary patterns;
“one person connects the representation of a certain word with
one thing, the other [person] with another thing…”
(B140). Hume's own paradigm for association in is the relations among
parts of a conversation (1748: §3). In such conversations, people
make different associations in the same circumstances. Kant's point is
that if the very paradigms for association fail to exhibit the sort of
necessity and universality at issue, then the hypothesis that
association is powerful enough to yield such an ordering of
representations — wherever we find it — is ruled
out. (Pereboom 1995; Dickerson 2004: 170–77; for an account of a
more general relationship in Kant between universality and necessity
on the one hand and apriority on the other, see Smit 2009).

Here we should see Kant as advancing his claim for the
applicability of the categories by ruling out association as an
explanation for (U-N). The structure of this (part of the) argument
can be represented as follows:

We have representations of objects, i.e., of objectively valid
phenomena. (premise)

All of our representations of objects are (in part) of universal
and necessary features of experience. (9, premise)

Necessary and universal features of experience cannot be explained
by association. (premise, from reflection on the nature of
association))

If (10) and (11) are true, all of our representations of objects
require a faculty for ordering mental states distinct from
association. (premise)

All of our representations of objects require a faculty for
ordering mental states distinct from association. (11, 12)

If (13) is true, all of our representations of objects require a
faculty for synthesis by a priori concepts. (premise)

All of our representations of objects require a faculty for
synthesis by a priori concepts. (13, 14)

We can expand (15) to explicitly note the link to the argument from above:

15*.

All of our representations of objects require a faculty for
synthesis by a priori concepts, the same faculty required to account
for my consciousness of the identity of myself as subject of different
self-attributions of mental states. (1-8, 13, 14)

To this we can add the final moves, which are explained in the
subsequent sections of the B-Deduction:

Insofar as our representations of objects require a faculty for
synthesis by a priori concepts, certain a priori concepts -- the
categories -- legitimately apply to these objects. (premise)

We have representations of objects, and they are all such that the
categories legitimately apply to these objects. (9, 15, 16)

The key necessary conditions, expressed by (12) and (14), like those
of the argument from above, are necessary conditions of only possible
explanation.

Guyer objects that at various places in the Transcendental Deduction
Kant illegitimately assumes knowledge of necessity, and perhaps this
argument falls to such a concern (Guyer 1987: 146–7). While this
concern has the potential of weakening Kant's argument, perhaps
Hume would not deny the necessity under consideration at this point in
the argument. Hume does maintain that it is in some sense impossible,
given an experience of constant conjunction, that the mind not be
carried from an impression of the first conjunct to an idea of the
next:

… having found, in many instances, that any two kinds of
objects, flame and heat, snow and cold, have always been conjoined
together; if flame or snow be presented anew to the senses, the mind is
carried by custom to expect heat or cold, and to believe, that
such a quality does exist, and will discover itself upon a nearer
approach. This belief is the necessary result of placing the mind in
such circumstances. It is an operation of the soul, when we are so
situated, as unavoidable as to feel the passion of love, when we
receive benefits; or hatred, when we meet with injuries. (1748:
§5)

Thus Hume himself contends that given certain specific empirical
circumstances, a particular type of ordering of perceptions in a sense
necessarily comes about.

A further concern of Guyer's is that Kant assumes without defense that
all knowledge of necessity is grounded in a priori concepts. But, in
response, perhaps we need not interpret Kant as arguing directly from
(U-N) to the claim that the categories correctly apply to objects in
our experience. Rather, we might see him as advancing his claim for
the applicability of the categories by ruling out association as an
explanation for (U-N). This transition can be divided into three
steps:

To explain the truth of (U-N), we must have a mental faculty
other than association for ordering representations.

This faculty does not consist solely of sensory items.

This faculty must employ a priori concepts, the categories in
particular.

The challenge Kant issues is to explain why, under normal
conditions, the ordering in question is universal and necessary. Part
of the best explanation, he believes, is (a), that we must have a
faculty for ordering the representations. Hume might agree with this
conclusion, supposing a sufficiently thin conception of
‘faculty’. Yet he would deny (b), that this faculty
does not consist solely of sensory items. Kant argues that the
Humean proposal for a faculty that consists solely of sensory items,
the faculty of association, cannot account for the truth of
propositions such as (U-N), for the very paradigms of association, such
as word association, and the association of topics in a conversation,
do not exhibit the requisite universality and necessity. The
alternative that can account for the truth of propositions such as
(U-N) involves affirming (c), that the faculty in question must be one
that employs the categories.

The associationist might counter that sensory experience is
sufficiently uniform for association to produce the universalities and
necessities at issue. Perhaps Kant is too quick to conclude that the
argument from universality and necessity is decisive, for in addition,
associationist objections of this sort must be answered — as
contemporary critical discussions of proposals for innate concepts indicate
(Pereboom 1995: 31–3). But this does not detract from the
anti-associationist force provided by the sorts of universalities and
necessities Kant has in mind, and this fact is recognized by the
contemporary discussion.

In §§19–20, Kant contends that the vehicle that brings
about the synthesis at issue is judgment, and that this vehicle
employs certain forms of judgment, which are in turn intimately
related to the twelve categories. By connecting synthesis to judgment
in this way, and the forms of judgment to the categories, Kant aims to
show that we must employ the categories in the synthesis of our
experience of objects.

In §19, Kant argues that there must be a certain way in which each
of my representations is unified in the subject, and he identifies this
way with judgment: “I find that a judgment is nothing but the manner in
which given cognitions are brought to the objective unity of
apperception” (B141). Judgment, Kant proposes, is objectively rather
than subjectively valid, and hence exhibits the type of universality
and necessity that characterizes objective validity (B142). He then
claims that without synthesis and judgment as its vehicle, an ordering
of representations might reflect what appears to be the case, but it
would not explain how we make distinctions between objective valid
phenomena (i.e., objects) and the subjective states they induce.

In §20, Kant ties this notion of judgment to the twelve forms of
judgment presented in the Metaphysical Deduction (A70/B95), and he then
connects these forms of judgment to the twelve categories
(A76–83/B102–9). The claim has often been made that the links Kant
specifies between synthesis and judgment, judgment and the forms of
judgment, the forms of judgment and the categories are not sufficiently
supported. Guyer, for example, argues that Kant has not adequately
established the last of these connections, that although Kant claims
that the categories are simply the forms of judgment as they are
employed in the synthesis of representations in an intuition
(A79/B104-A80/B105, B143), he has failed to make this claim plausible
(Guyer 1987: 94–102). It is fair to say that these concerns have merit.
Kant's assertions about these ties remain more obscure than the
preceding part of the Transcendental Deduction, and it continues to be
a serious challenge for interpreters to clarify and vindicate them.

Béatrice Longuenesse (1998), in her interpretation of the
Metaphysical Deduction, takes up this challenge. In her view, the
faculty at issue in the production and use of concepts, the
understanding, is the power to judge (Vermögen zu
Urteilen), which is ultimately a disposition or a conatus
to make judgments and to shape how we are affected so that we can make
them (Longuenesse 1998: 208, 394). The logical forms of judgment are in
essence the forms of combination of concepts in judgments. One such
form is the categorical, which is the form of subject-predicate
judgments; another is the hypothetical, the form of conditional
judgments. Kant contends that the logical form of a judgment is what
makes it capable of truth or falsity, for by means of such a form a
judgment can constitute a relation of a subject's representations
to an objective feature of reality (Longuenesse 2000, 93–4). For
instance, by its categorical form, the judgment ‘the boat is
moving’ can constitute the relation of my representations of a
boat and of motion to an objectively existing boat in motion, and as a
result this judgment can be true or false.

One role of the logical forms of judgment is in the process of
analysis, by which the objects we intuit are subsumed under concepts.
What results from this process is a judgment that expresses what Kant
calls an analytic unity — paradigmatically, the unity in
the subsumption of several intuited objects under a single concept. But
a logical form of judgment can also function in a different role: in
the synthesis of a manifold of an intuition. The result in this case is
a synthetic unity, the unity of a synthesized multiplicity of
representations in a single intuition. The understanding, as the power
to judge, functions in each of these two roles; “the same
function that gives unity to concepts in judgment, also gives unity to
the mere synthesis of representations in intuition” (A79/B104–5).
In its synthetic role, the understanding adds content to the forms of judgment:

The same understanding, and indeed by means of the very same actions
through which it brings the logical form of judgment into concepts by
means of the analytical unity, also brings a transcendental content
into its representations by means of the synthetic unity of the
manifold in intuition in general. (A79/B105)

The addition of such transcendental content turns the form of judgment into a category. This content is a feature of the forms of intuition, space and time, which are called upon when
the power to judge sets out to unify a manifold of intuition (B128–9).
The categories — more precisely, the versions of the categories
that are schematized for our way of cognizing (A137/B176ff) — are thus
generated from the forms of judgment in the process of synthesizing
intuitions by the addition of spatial and temporal content. For
example, generated from the categorical form of judgment by the
addition of such content is the category of substance, and generated
from the hypothetical form of judgment in this way is the category of
cause. (For beings possessing the power of understanding but with
different forms of intuition, the categories would be schematized
differently from ours.)

In §20 Kant, draws a conclusion from the considerations he has so
far advanced: “Consequently, the manifold in a given intuition is
necessarily subject to the categories” (B143). One might think that
this is precisely what Kant intended to establish in the Transcendental
Deduction, and thus that the argument is brought to an end in §20.
However, in §21 he indicates that the Deduction is not yet
complete: “Thus in the above proposition a beginning is made of a
deduction of the pure concepts of understanding” (B144). Kant
goes on to explain:

In what follows (cf. §26) it will be shown, from the mode in
which the empirical intuition is given in sensibility, that its unity
is no other than that which the category (according to §20)
prescribes to the manifold of a given intuition in general. Only thus,
by demonstration of the a priori validity of the categories in respect
of all objects of our senses, will the purpose of the deduction by
fully attained. (B144–5)

Here a perennial interpretive question arises: how should we
construe the argument we find in §26, together with material from
§24, which is sometimes designated as the second step of the
B-Deduction?

One position on this interpretive issue is advanced by Erich Adickes
(1889: 139–4) and H. G. Paton (1936: v. 1, 501), who argue that while
the material that precedes §21 constitutes an objective
deduction, material in §24 and §26 comprise a
subjective deduction. This distinction has its source in the
Preface to the A edition:

This enquiry, which is somewhat deeply grounded, has two sides. The
one refers to the objects of pure understanding, and is intended to
expound and render intelligible the objective validity of its a
priori concepts. It is therefore essential to my purposes. The
other seeks to investigate the pure understanding itself, its
possibility and the cognitive faculties upon which it rests: and so
deals with it in its subjective aspect. Although this latter
exposition is of great importance for my chief purpose, it does not
form an essential part of it. (Axvi-xvii)

Henrich (1968–69) rejects the Adickes/Paton proposal for the
reason that in §21 Kant states that the demonstration of the
validity of the categories is completed only in §26, and the
passage from the A-Preface indicates that this is a task for the
objective deduction. In defense of Adickes and Paton, in §20 Kant
claims to have established that the categories apply to the manifold
in any one given intuition, and affirms that he will now show that
categories apply to any object presented to the senses. In view of the
aim of the objective deduction, this move would seem to require only a
straightforward and trivial application of the result of §20 to
any empirical intuition we might have (Dickerson 2004:
195–96). So, on a charitable interpretation of Kant's agenda,
showing that the categories apply to any object presented to the
senses plausibly involves considerations beyond the scope of the
objective deduction.

Henrich points out that although in the B-Deduction Kant sought to
avoid the problems of a subjective deduction, this “does not
mean that he neglected the demand for an explanation of the
possibility of relating the categories to intuitions.” However,
by Kant's account, a subjective deduction features not only an
examination of cognitive faculties, but also an investigation of
“the possibility of the pure understanding,” which would
include an investigation of how the categories are related to
empirical intuition and to the objects presented to us in such
intuition. This is precisely the type of inquiry that we encounter in
§24 and §26 — and Henrich agrees. Thus, in the last
analysis, it seems that the views of Henrich, Paton, and Adickes can
be reconciled: they concur that the second step aims to show how it
is that the categories are related to objects of experience -- in such
a way as to show how the categories correctly apply to them. Moreover,
this common ground yields a satisfying interpretation of the specifics
of the text. In §26 Kant contends that our intuitive
representations of space and time, since they themselves contain a
manifold, must also be synthesized by means of the categories. And
now, because all objects that can be presented to us in intuition are
given to us in space and time, our representations of these objects will
also be synthesized by the categories. Kant thus provides an
explanation of how the categories apply to all the objects that can be
presented to the senses, or in experience, by way of the manner in
which these objects are given to us (cf. Longuenesse 1998:
211–33; Keller 1998: 88–94; Dickerson 2004: 196–201;
Pollok 2008).

The text of the second step gives rise to a number of general
important interpretive issues for Kant's overall position. One such
issue, raised by the complex footnote at B160-61, is whether Kant
countenances a kind of unity in our representations which is not a
result of synthesis by a priori concepts, but is instead an upshot of
the forms of intuition (McLear 2014) or of the productive imagination
independently of the categories (Heidegger 1929/1997; cf., Longuenesse
1998). What one concludes about the footnote has implications for
whether Kant is a conceptualist or a nonconceptualist about intuitions
or our representations of objects (Hanna 2008, 2011, Grüne 2011,
Schulting 2012, McLear 2014). Robert Hanna (2011) argues that the possibility
of nonconceptual intuition results in a gap in the argument of the
B-Deduction, since this would allow for intuitions to which the
categories do not apply. Stefanie Grüne (2011) and Schulting (2012) oppose this line of reasoning.

In the transcendental argument of the Refutation of Idealism,
Kant's target is not Humean skepticism about the applicability of
a priori concepts, but rather Cartesian skepticism about the external
world. This argument was added by Kant to the second edition of the
Critique of Pure Reason (B274–279, with a change
suggested in the Preface to B, Bxxxix-Bxli), and subsequently
embellished and reworked in a series of Reflections (Guyer 1987:
279–316). More specifically, Kant intends to refute what he
calls problematic idealism, according to which the existence of
objects outside us in space is “doubtful and
indemonstrable” (B274). His strategy is to derive the claim that
such objects exist from my awareness that my representations have a
specific temporal order. At the present time I am aware of the
specific temporal order of many of my past experiences, an awareness
produced by memory. But what is it about what I remember that allows
me to determine the temporal order of my experiences? There must be
something by reference to which I can correlate the remembered
experiences that allows me to determine their temporal order. But
first, I have no conscious states that can play this role. Further,
this reference cannot be time itself, for “time by itself is not
perceived;” Kant argues for this claim in the First Analogy
(B224–5). As Guyer puts it, it is not as if the content of
memories of individual events are manifestly indexed to specific times,
as sportscasts and videotapes often are (Guyer 1987:
244). Kant contends that the only other candidate for this reference
is something outside of me in space, and it must be something
(relatively) permanent (cf. First Analogy, B224–5). Perhaps this
claim is made plausible by how we often actually determine the times
at which our experiences occur. We use observations of sun's
positions, or of a clock that indicates time by way of the period of a
pendulum, or by the period of the vibration of a cesium atom. Kant's
argument can be seen as exploiting this fact, together with the
observation that there is no similar periodic process in human
conscious experience considered independently of any spatial objects
it might represent, and that we lack any awareness of time by itself,
to show we must perceive objects outside us in space by reference to
which we can determine the temporal order of our past experiences.

I am conscious of my own existence in time; that is, I am aware,
and can be aware, that I have experiences that occur in a specific
temporal order. (premise)

I can be aware of having experiences that occur in a specific
temporal order only if I perceive something permanent by reference to
which I can determine their temporal order. (premise)

No conscious state of my own can serve as the permanent entity
by reference to which I can determine the temporal order of my
experiences. (premise)

Time itself cannot serve as this permanent entity by reference
to which I can determine the temporal order of my experiences.
(premise)

If (2), (3), and (4), are true, then I can be aware of having
experiences that occur in a specific temporal order only if I perceive
persisting objects in space outside me by reference to which I can
determine the temporal order of my experiences. (premise)

Therefore, I perceive persisting objects in space outside me by reference
to which I can determine the temporal order of my experiences.
(1–5)

Several points of interpretation should be noted. First, it is
generally agreed that the notion of awareness in Premise (1) should be
interpreted as a success notion, i.e., that to be aware that I have
experiences that occur in a specific temporal order is to correctly
determine that they occur in this order (Allison 1983: 290ff, Guyer
1987: 293ff, Dicker 2004, 195ff., 2008; Chignell 2010). Second, most
commentators concur that the experiences at issue are my past
experiences. Guyer suggests that the argument might be extended to
combinations of my past and my present experience, but Dicker objects
that the fact that past experiences occurred before the present one is
directly knowable by introspection, and so doesn't require the
external reference (Guyer 1987; Dicker 2004: 195ff.). Third, Jonathan
Bennett points out that we have single memories whose content spans an
appreciable length of time that allow us to determine the order of
past mental states . When one remembers hearing a certain word, one
can accurately determine by the content of a single memory that
certain phoneme-experiences occurred prior to other
phoneme-experiences — for example, that one heard
‘mad’ and not ‘dam’ (Bennett 1966:
228–9). Dicker (2004: 201–2) remarks that we may be able
to determine accurately the order some of our past states by means of
such memories, but we cannot ascertain the order of most of our past
experiences in this way. He therefore advocates a restriction of the
argument to the experiences we can correctly order but not in the way
Bennett adduces. Fourth, many commentators have noted that we might
have perceived time directly. Guyer, as we just saw, suggests that all
of our conscious experiences might have featured a time clock, much
like a television sportscast or a video camera (1987: 244;
cf. Strawson 1966). But as Dicker points out, in actual fact our
experience does not have any such feature, and he is content for
Premise (4), that time itself cannot serve as the reference whereby I
correctly determine the temporal order of my past experiences, to
state a merely contingent fact about us (2004, 2008). Chignell (2010)
expresses a concern about interpretations of the Refutation in which
it is merely a contingent fact about us that the alternative methods
for determining the temporal order of my past experiences are
unavailable, for then the conclusion, that we perceive objects in
space, would inherit such mere contingency, which he argues to be at
odds with Kant's hopes for the Refutation. Fifth, commentators differ
on the relation that must obtain between the objects in space and the
experiences whose temporal order we can correctly determine. Guyer
argues that the relation must be causal, since “the states of
the self are judged to have a unique order just insofar as they are
judged to be caused… by the successive states of enduring
objects” (Guyer 1987: 309; cf. Dicker 2004: 200, 2008). By
contrast, in Allison's view we require the temporal order of objects
in space only as a backdrop against which to determine the temporal
order of our experiences; “an enduring, perceivable object (or
objects) is required to provide a frame of reference by means of which
the succession, coexistence, and duration of appearances in a common
time can be determined” (Allison 1983: 201). If the object in
space that provides the reference is the sun, for example, the states
of the sun don't need to cause my experiences for me to determine
their temporal order by means of those states.

Three of the most pressing problems that have been raised for the
Refutation are the following. First, a skeptic might well reject
Premise (1) on the ground of a general skepticism about memory
(Allison 1983: 306–7). Bertrand Russell, for example, suggests
that for all I know I was born five minutes ago (Russell 1912). On
this skeptical hypothesis, I would be mistaken in my belief that I had
experiences A, B, and C which occurred more than five minutes ago,
first A, then B, and lastly C. Plausibly, a skeptic who claimed that
we lack adequate justification for a belief that external objects
exist would likely also be disposed to claim that I lack justification
for my belief that I had experiences that occurred in the past in that
specific temporal order. Thus Kant's supposition that Premise (1)
yields leverage against an external-world skeptic is mistaken
(cf. Dicker 2008, Chignell 2010).

Second, consider the claim that my mental states (or the mental
subject itself) are as suited as objects in space to function as a
reference whereby I can correctly judge the temporal order of my past
experiences. Suppose I had available as such a reference only the mere
mental appearance of a digital clock in one corner of my field of
consciousness. This would not clearly be less effective than an actual
clock in space. To this one might reply, with Dicker, that there are no
actual mental states that are adequate to serve as such a reference.
However, and this is the deeper worry, on Berkeley's idealist view
according to which the esse (to be) of objects in space is
their percipi (to be perceived), any spatial objects would be
nothing more than mental states of some subject, or aspects of those
states, but Berkeleyan spatial perceptions would be as adequate a
reference by which to determine the temporal order of my past
experiences as perceptions of spatial objects that are in some sense
distinct from my mental states (cf. Allison 1983: 300–1; Vogel 1993;
Chignell 2010).

Third, one might contend that Kant's Refutation demonstrates
that the reference in question must be (relatively) permanent, and that there is
nothing in the Berkeleyan spatial realm that satisfies this
requirement. However, to this one might respond that the reference
by which I determine the temporal order of my past experiences need not
be permanent in a way that cannot be satisfied by Berkeleyan spatial
objects. If in the corner of my field of consciousness featured
distinct momentary flashes, every second, indicating the date and time
to the second, I would be able to determine the temporal order of my
past experiences by their means (cf., van Cleve, reported in Dicker
2004: 207).

A note on the second of these concerns: Several commentators have
argued that Kant's Refutation of Idealism is meant to undermine any
metaphysical sort of idealism, including metaphysical idealisms that
have been attributed to Kant (Guyer 1987: 317–29). But while
this reading has interesting support, one should hesitate to endorse
it solely on the ground that Kant maintains that spatial objects are
distinct from the states of the perceiver. On a plausible metaphysical
interpretation of Kant's idealism, the esse of objects in
space is not their percipi, since Kant's spatial objects, by
contrast with Berkeley's, are recognition-transcendent. In Berkeley's
position, a subject's perception of an oar in the water as crooked is
not a misperception, for “what he immediately perceives by sight
is not in error, and so far he is in the right,” and it is
misleading only because it is apt to give rise to mistaken inferences
(Berkeley 1713: Third Dialogue); while for Kant this perception is in
error. In Kant's view, the oar is recognition-transcendent by virtue
of the Second Postulate's provision that the actuality of such objects
is determined causally:

That which is bound up with the material conditions of experience,
that is, with sensation, is actual
(wirklich). (A218=B266)

The actual is that which conforms to the system of empirical causal
laws (A225/B272ff.), and because the crookedness of the oar does not so
conform, it is not actual. How the Second Postulate rules out the
existence of the apparent spatial objects of dreams and hallucinations
is spelled out in the third note to the Refutation of Idealism:

Note 3. From the fact that the existence of outer things is required
for the possibility of a determinate consciousness of the self, it
does not follow that every intuitive representation of outer things
involves the existence of those things, for their representation can
very well be the product merely of the imagination (as in dreams and
delusions). Such representation is merely the product of previous
outer perceptions, which, as has been shown, are possible only through
the reality of outer objects… Whether this or that supposed
experience be not purely imaginary, must be ascertained from its
special determinations, and through its congruence with the criteria
of all actual experience (wirklichen Erfahrung). (B278–9
cf.A376, cf. A492=B520–1)

The objects of dreams and hallucinations don't meet the criterion of
actuality of the Second Postulate, that is, according with the laws of
causality. Thus while in Berkeley's view the esse of spatial
things consists in their being perceived by the senses, for Kant they
are the objects of the correct causal/scientific account of the
contents of our outer experience. This causal criterion allows that a
spatial object, or, more precisely, the matter from which it is
constituted, is (at least relatively) permanent — which would
seem ruled out in Berkeley's position, since the spatial object does
not last any longer than the idea does. (Berkeley does say that the
ideas of what “are called real things” differ from
“those excited in the imagination” by “being less
regular, vivid, and constant” (Berkeley
1710, Principles Part I, 33), but for him this difference
does not challenge or undermine the claim that the esse of a
physical object is its percipi.) None of this forces a
metaphysical realist as opposed to an idealist reading of Kant.

Yet at the same time, according to the second concern, the Refutation
is inadequate even if its ambition is restricted to demonstrating the
existence of merely metaphysically ideal but nonetheless
recognition-transcendent objects outside us in space. For granting
that the Refutation establishes that for me to determine the temporal
order of my past experiences I must perceive objects in space, it
fails to show that I need to perceive spatial objects any more
realistic than the Berkeleyan ones. More generally, the worry is that
Berkeleyan version of idealism has the resources to yield as adequate a
reference for me to determine the temporal order of my past
experiences as any rival position Kant is plausibly interpreted as
endorsing, and that for this reason the Refutation falls short of its
aim.

Kant-inspired transcendental arguments against skepticism about the
external world were developed with vigor in the mid-twentieth century,
notably by P. F. Strawson, most famously in his Kantian reflections in
The Bounds of Sense (1966). These arguments are often
reinterpretations of, or at least inspired by, Kant's
Transcendental Deduction and his Refutation of Idealism. Some are more
ambitious than Kant's would seem to be, insofar as they attempt
to refute some variety of skepticism by showing that there is an
essential commitment of the skeptical position for which the falsity of
that position is a necessary condition (Nagel 1997: 60ff.).
Strawson's most famous transcendental argument (1966: 97–104) is
modeled on the Transcendental Deduction, but explicitly without a
commitment to synthesis or any other aspect of Kant's
transcendental psychology. His target is a purely sense-datum
experience, which does not feature objects, “conceived of as
distinct from any particular states of awareness of them,” that
is, a Berkeleyan experience of spatial objects whose esse is
percipi (1966: 98). The core of the argument is as follows.
From the premise that every (human) experience is such that it is
possible for its subject to become aware of it and ascribe it to
herself, we can infer that in every experience the subject must be
capable of distinguishing a recognitional component not wholly absorbed
by, and thus distinct from, the item recognized (1966: 100). From this
we can infer that the subject must conceptualize her experiences in
such a way so as to contain the basis for a distinction between a
subjective component — how the experienced item seems to the subject,
and an objective component — how the item actually is. Strawson
specifies that “collectively,” this comes to “the
distinction between the subjective order and arrangement of a series of
such experiences on the one hand, and the objective order and
arrangement of the items of which they are the experiences on the
other” (1966: 101). Conceptualizing experience as involving an
objective order and arrangement of items amounts to making objectively
valid judgments about it, which, in turn, implies that experience must
consist of a rule-governed connectedness of representations (1966: 98).
Summarizing, from a premise about self-consciousness, we can infer that
the subject must conceptualize her experience so as to feature a
distinction between “the subjective route of his experience and
the objective world through which it is a route,” where the
experience of the objective world consists in a rule-governed order of
representations (1966: 105).

Barry Stroud, in his 1968 article “Transcendental
Arguments,” issued a formidable challenge to the enterprise of
defeating the external-world skeptic by transcendental arguments of
this sort (Stroud 1968). There Stroud contends that such transcendental
arguments are undermined by a problem which can be stated quite
generally. These arguments feature reasoning from some aspect of
experience or knowledge to the claim that the contested feature of the
external world in fact exists. In each case the existence of
the external feature will not be a necessary condition of the aspect of
experience or knowledge in question, for a belief about the
external feature would always suffice. Although the claim about
existence of the aspect of the external world could be secured if
certain kinds of verificationism or idealism were presupposed, these
views are highly controversial. Besides, one could make as much of an
inroad against the skeptic armed with the verificationism or idealism
alone, without adducing the transcendental argument at all (cf.
Brueckner 1983, 1984).

Although Strawson's transcendental argument in The Bounds of
Sense is not a specific target in Stroud's (1968), Anthony
Brueckner suggests that it is susceptible to the line of criticism
that Stroud develops (Brueckner 1983: 557–8). For, arguably,
Strawson can only conclude that experience must be conceptualized in a
certain way, such as to allow the subject to make the distinction
between an objective world and her subjective path through it. This is
not a conclusion about how a mind-independent world must be, but only
about how it must be thought. (Alternatively, Strawson might be read
as drawing only a conclusion about how experience must be
conceptualized, which would render the transcendental argument as one
of a more modest variety (see below)).

Recent developments of transcendental arguments reflect a struggle to
accommodate Stroud's criticism, and often chastened expectations
about what such arguments might establish by way of refuting
skepticism. One more modest sort of transcendental argument begins with
a premise about experience or knowledge that is acceptable to the
skeptic in question, and then proceeds not to the existence of some
aspect of the external world, but in accord with Stroud's
criticism, to a belief in the existence of some aspect of the external
world. Stroud himself advocates a strategy of this sort (Stroud 1994,
1999), as does Robert Stern (1999b). The kind proposed by Stroud begins
with the premise that we think of the world as being independent of us,
and it concludes, as a necessary condition of this premise, that we must
think of it as containing enduring particulars. Such an argument does
not claim that as a necessary condition of this premise there must
exist such particulars. It contends only for “a connection solely
within our thought: if we think in certain ways, we must think in
certain other ways” (Stern 1999b: 165). A belief or thought to
which one reasons in this way would, in Stroud's conception, have
a certain indispensability, “because no belief that must
be present in any conception or any set of beliefs about an independent
world could be abandoned consistently with our conception of the world
at all,” and it would be invulnerable “in the
special sense that it could not be found to be false consistently with
its being found to be held by people” (Stern 1999b: 166).

Stern advances a conception of this kind of argument on which it
addresses a skeptic who questions whether certain beliefs cohere with
others in one's set, as opposed to a skeptic who questions whether
certain beliefs are true (Stern 1999b). A modest transcendental
argument would then aim to show that a belief whose coherence with the
other beliefs is challenged so coheres after all. The requisite
coherence might be demonstrated by showing that the belief in question
is actually a necessary condition of a belief that is indispensable
(in some coherentist sense) to one's set. Mark Sacks (1999) objects
that if at the same time one were to admit that the belief might not
be true, one's sense that one is justified in holding the belief would
be undermined. This worry is a serious one. Sacks argues that it
arises because of a tension between the coherentist theory of
justification and the realist correspondence theory of truth that the
external world skeptic presupposes. One might respond, he points out,
by accepting a coherence theory of truth as well, but this would be to
adopt a version of idealism. Moreover, it seems that Sacks's proposal
would not solve the problem, for the reason that even if one accepted
a coherence theory of truth, one would still have to admit that for
specific instances of a belief one might be mistaken, even if one
maintained that one was justified in holding that belief on grounds of
coherence.

An important criticism of Stroud's proposed sort of modest
transcendental argument is raised by Brueckner (1996). Brueckner
addresses the fit between the claim that certain non-skeptical beliefs
are invulnerable in Stroud's sense, and the admission that they
might not be true. More precisely, he challenges the claim that one can
simultaneously affirm the following two principles, each gleaned from
Stroud (1994):

(CT) If we attribute beliefs to speakers (if we believe that they
have beliefs with determinate contents), then we must also believe that
there is an independent world of enduring objects with which they
interact.

and

(SK) Although we believe many things about a world independent of us
and our experiences, … none of those beliefs is true.

Brueckner divides (SK) into

we believe many things about an external reality independent of
us and our experiences

and

none of these beliefs is true.

Stroud argues, in effect, that given CT we cannot believe that (i) and
(ii) are true, but nonetheless, we can believe that (i) and (ii) are
logically compossible given CT. Brueckner argues that using similar
reasoning, given CT we cannot conceive of a possible world in which
both (i) and (ii) hold, and this fact undermines Stroud's claim. To
conceive of a world W in which (i) is true is to conceive of a world
in which we (in the actual world) attribute beliefs about
mind-independent objects to counterfactual versions of us (CVs) in W.
But given CT, we must now also conceive of W as featuring
mind-independent objects with which these CVs interact. Consider the
CVs' belief that there exist mind-independent objects —
a belief they share with us. This belief of theirs will be true. And
thus in W (ii) will be false. Hence we have not conceived of a world
in which given CT, SK is nevertheless true, and indeed, we will not be
able to conceive of such a world. But our not being able to conceive
of a possible world in which given CT, SK is true, constitutes strong
evidence against the claim that SK is logically possible given CT
(1996: 274–75). Brueckner does not think that this argument
demonstrates that it is inconsistent to accept CT and assert that SK
is logically possible, but that there will be no evidence of the usual
kind for this claim — evidence from conceivability. Thus given
the transcendental argument he advances, Stroud will be pushed in the
direction of the immodest conclusion that it is not possible for us to
be mistaken in our belief that there exist mind-independent
objects.

From this one might be tempted to conclude that despite his critique of
1968, Stroud, with Brueckner's assistance, has found a
transcendental argument that does in fact establish a conclusion about
the external world. However, so far nothing has been said to turn back
Stroud's 1968 critique, and it seems much more likely that the
argument Stroud now advances can at best conclude with a version of CT
in which the term “independent” must be read in a
transcendentally ideal sense — in which, for example, the nature of
certain physical objects is determined by our best scientific theories
about them, and our sensory experiences can be in error about these
objects. And if this is so, then the argument would secure a belief
about the external world only on the presupposition of metaphysical
idealism, and this is one of the ways in which anti-skeptical
transcendental arguments might be doomed according to Stroud's
1968 critique.

Despite these sorts of challenges, the aspiration to forge transcendental
arguments with considerable anti-skeptical force has not waned.
Qassim Cassam (1999), Sacks (2000), and Stern (2000), for
example, have developed creative and nuanced versions
of transcendental arguments designed to negotiate the type of problem
Stroud has pressed.

The legacy of the arguments such as the Transcendental Deduction and
the Refutation of Idealism includes not only Kant's actual
successes, but also a number of influential philosophical strategies:
the now-standard tactic of arguing for concepts whose
source is in the mind from universal and necessary features of
experience; the idea of drawing significant philosophical conclusions
from premises about self-consciousness alone; and the notion of a
transcendental argument, which from an uncontroversial premise about
our thought, knowledge or experience, reasons to a substantive and
unobvious presupposition and necessary condition of this claim.

1781/1787, Critique of Pure Reason (trans. P.
Guyer and A. Wood). Cambridge and New York: Cambridge University Press,
1987. (References to CPR are in the standard pagination of the
1st (A) and 2nd (B) editions. A reference to only
one edition means that the passage appeared only in that edition.)

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